Fluorophore-mediated, fiber-optic, multi-analyte, immunosensing system for rapid diagnosis and prognosis of cardiovascular diseases

Biosensors for natriuretic peptides in cardiovascular diseases. A review

Heart failure (HF) is a complex clinical syndrome associated with high rates of morbidity and mortality. Over the years, it has been crucial to find accurate biomarkers capable of doing a precise monitor of HF and provide an early diagnosis. Of these, it has been established an important role of natriuretic peptides in HF assessment. Moreover, the development of biosensors has been garnering interest as new diagnostic medical tools. In this review we first provide a general overview of HF, its pathogenesis, and diagnostic features. We then discuss the role of natriuretic peptides in heart failure by characterizing them and point out their potential as biomarkers. Finally, we adress the evolution of biosensors development and the available natriuretic peptides biosensors for disease monitoring.

A review of biosensors for the detection of B-type natriuretic peptide as an important cardiovascular biomarker

Heart disease, as the most serious threat to human health globally, is responsible for rising mortality rates, largely due to lifestyle and diet. Unfortunately, the main problem for patients at high risk of heart disease is the validation of prognostic tests. To this end, the detection of cardiovascular biomarkers has been employed to obtain pathological and physiological information in order to improve prognosis and early-stage diagnosis of chronic heart failure. Short-term changes in B-type natriuretic peptide are known as a standard and important biomarker for diagnosis of heart failure. The most important problem for detection is low concentration and short half-life in the blood. The normal concentration of BNP in blood is less than 7 nM (25 pg/mL), which increases significantly to more than 80 pg/mL. Therefore, the development of new biosensors with better sensitivity, detection limit, and dynamic range than current commercial kits is urgently needed. This review classifies the biosensors designed for detection of BNP into electrochemical, optical, microfluidic, and lateral-flow immunoassay techniques. The review clearly demonstrates that a variety of immunoassay, aptasensor, enzymatic and catalytic nanomaterials, and fluorophores have been successfully employed for detection of BNP at low attomolar ranges. Dtection of B-type natriuretic peptide with biosensors.

Quantification of cardiac biomarkers using label-free and multiplexed gold nanorod bioprobes for myocardial infarction diagnosis

Gold nanorod (GNR) is an attractive optical transducer for label-free biosensing owing to the localized surface plasmon resonance (LSPR) which is highly sensitive to the dielectric constant of the surrounding medium modulated by biological bindings. By adjusting the nanorod aspect ratio (length to width ratio), desired absorption wavelength can be continuously tuned from 600 to 1100 nm. Here we demonstrated a linear relationship between the aspect ratio and the LSPR peak wavelength. Taking advantage of this tunability feature, we developed a multiplexed GNR sensor by combining nanorods with distinct LSPR wavelengths. Specifically, GNRs of AR 2.1 and 4.2 exhibiting longitudinal plasmonic band of 640 and 830 nm, respectively, were functionalized with specific antibody. Concentrations of multiple analytes were measured by correlating to the spectral shift at the distinct plasmon band maxima upon specific binding. The practical use of this mixed bioprobes for simultaneous quantification of cardiac biomarkers (myoglobin and cardiac troponin I) in the clinically significant sensing range was described. The LSPR red shift magnitude is linearly proportional to the increase in the target analyte concentration (R(2)=0.98). The calibration curve can clearly differentiate varying biomarker amounts with a high specificity. For multiplexed biosensing, the plasmon shift at the dedicated peak wavelength can be specifically correlated with spiked biomarker for simultaneous detection in the sample mixture. This technology can be further transformed onto miniaturized biochips based on the nanosized optical transducer to allow point-of-care blood testing for risk stratifications of cardiac patients in clinical settings.

Magnetic nanoparticle mediated enhancement of localized surface plasmon resonance for ultrasensitive bioanalytical assay in human blood plasma

We demonstrate that Fe(3)O(4) magnetic nanoparticle (MNP) can greatly enhance the localized surface plasmon resonance (LSPR) of metal nanoparticle. The high refractive index and molecular weight of the Fe(3)O(4) MNPs make them a powerful enhancer for plasmonic response to biological binding events, thereby enabling a significant improvement in the sensitivity, reliability, dynamic range, and calibration linearity for LSPR assay of small molecules in a trace amount. Rather than using fluorescence spectroscopy or magnetic resonance imaging, this study marks the first use of the label-free LSPR nanosensor for a disease biomarker in physiological solutions, providing a low cost, clinical-oriented detection. This facile and ultrasensitive nanosensor with an extremely light, robust, and low-cost instrument is attractive for miniaturization on a lab-on-a-chip system to deliver point-of-care medical diagnostics. To further evaluate the practical application of Fe(3)O(4) MNPs in the enhancement of LSPR assay, cardiac troponin I (cTnI) for myocardial infarction diagnosis was used as a model protein to be detected by a gold nanorod (GNR) bioprobe. MNP-captured cTnI molecules resulted in spectral responses up to 6-fold higher than direct cTnI adsorption on the GNR sensor. The detection limit (LOD) was lowered to ca. 30 pM for plasma samples which is 3 orders lower than a comparable study. To the best of our knowledge, this marks the lowest LOD for a real plasma protein detection based on label-free LSPR shift without complicated instrumentation. The observed LSPR sensing enhancement by Fe(3)O(4) MNPs is independent of nonspecific binding.

Theory, experiment, and application of optical fiber etching

Based on fiber Bragg grating (FBG), an online monitoring system for the etching process of optical fiber in a hydrofluoric (HF) acid solution has been designed. The variation curves of the wavelength shifts of FBGs with etching time at three different temperatures have been obtained and analyzed theoretically. The results show that the etching process of optical fiber in HF acid solution can be understood by the variation of the wavelength shift of FBG with etching time. Finally, required tapered fiber tips can be made by controlling the etching velocity and the pulling velocity of optical fiber from the etching solution.

Theoretical investigation for excitation light and fluorescence signal of fiber optical sensor using tapered fiber tip

For fiber optical sensor made of tapered fiber tip, the effects of the geometrical parameters of tapered tip on two important factors have been investigated. One factor is the intensity of the evanescent wave into fluorescent layer through core-medium interface; the other is the intensity of fluorescence signal transmitted from fluorescent layer to measurement end. A dependence relation of the intensity of fluorescence signal transmitted from fluorescent layer to measurement end upon the geometrical parameters of tapered tip has been obtained. Theoretical results show that the intensity of the evanescent wave into fluorescent layer rises with the decrease of the end diameter of tapered tip, and the increase of the tip length; and the transmitted power of fluorescence signal increases linearly with the increase of the tip length due to the contribution of the side area of tapered tip.

Near real-time immuno-optical sensor for diagnosing single point mutation: a model system: sensor for factor V Leiden diagnosis

Factor V leiden (FVL) is an abnormality of factor V (FV), a blood coagulation factor. It is a hereditary blood coagulation disorder with a high frequency (3-7% of general population). The most common type of FVL is caused by a single amino acid mutation and, therefore, its diagnosis is currently done only by DNA analysis, which takes a long time and is expensive. We have developed a rapid, accurate, and cost-effective, sandwich immuno-optical sensing method. To produce monoclonal antibodies against FV or FVL, having minimal cross-reactivity with the other molecule, a 20 amino acid sequence (20-mer) of FV or FVL at around the mutation site was utilized. The antibodies were screened first with the 20-mers and then the ones showing no cross-affinity were reacted with native FV or FVL molecules and they showed some cross-reactivity. Using two antibodies having strongest affinity to either FV or FVL molecule, a FV and a FVL preferred sensors, were produced. After verifying that the levels of the antibody affinity to the two different molecules remained constant with changes in analyte concentration, a two-sensor system is developed to quantify FV and FVL in plasma samples. The system quantified the levels of FV and FVL at the maximum error of 0.5 microg/ml-plasma, in their physiological concentration range of 0-12 microg/ml-plasma. The levels of both molecules may provide us whether the patient has FVL or not but also the seriousness level of the disease (homozygous and different level of heterozygous).

Multiplexed spectroscopic detections

This review describes various platforms used for multiplexed spectroscopic analysis. We highlight the use of different types of spectroscopy for multiplexed detections, including Raman spectroscopy, surface-enhanced Raman spectroscopy, surface plasmon resonance, and fluorescence. This review also explores the use of cross-reactive sensors in combination with pattern-recognition algorithms to monitor multiple analytes in aqueous and vapor matrices. It also discusses applications of these techniques, paying special attention to their use in the detection of biologically relevant analytes.

Clinical validation of fiberoptic immunobiosensor for point-of-care analysis of plasma nerve growth factor

BACKGROUND

Upregulation of plasma nerve growth factor (NGF) is indicative of cardiac nerve sprouting that is underlying the mechanisms for cardiac arrhythmias. A conventional assay method (e.g., enzyme-linked immunosorbent assay [ELISA]) is usually time consuming and technically complicated for NGF analysis for potential arrhythmia prognosis.

OBJECTIVE

This study is to develop a rapid and and reliable assay method for point-of-care (POC) testing of plasma NGF.

METHODS

We recently developed a fiberoptic immunobiosensor for point-of-care testing of human plasma NGF. Physiological concentrations of NGF (1 to 200 ng/ml) could be quantified in both buffer and human blood plasma samples (100 microl) within 5 min. The intra-assay coefficient of variation was 5%, and the interassay coefficient of variation was 8%. The clinical utility of the NGF biosensor was evaluated using clinical blood samples from atrial fibrillation patients (n = 21). Peripheral venous blood was sampled before and immediately after radiofrequency ablation and again at postoperative day 1.

RESULTS

The NGF level did not change significantly between before (15.73 +/- 16.67 ng/ml) and immediately after radiofrequency ablation (13.58 +/- 11.45 ng/ml, P = NS); however, there was a significant elevation to 28.41 +/- 19.52 ng/ml in postoperative day 1 (P <.01). In a follow-up study (11 +/- 1 months), the increased magnitude in patients with atrial fibrillation recurrence (4.1-fold +/- 1.96-fold) was significantly higher than those without (1.72-fold +/- 0.53-fold; P <.001). The results were highly comparable to those of the ELISA analysis.

CONCLUSION

Because of the comparable data accuracy and much faster assay time as compared with ELISA, the fiberoptic biosensor is promising as a clinical POC assay method for plasma NGF analysis at patient bedsides for potential cardiac disease diagnosis and prognosis.

Anticoagulant blood factor deficiencies (protein C)

Anti-coagulant proteins are essential to maintain blood hemostatis for the supply of oxygen and nutrients to tissue cells and for the removal of toxic by-products from metabolism. Hereditary or acquired deficiencies of Protein C, Protein S, or Antithrombin III can lead to disease states such as deep vein thrombosis (DVT) with the possibility of producing lung emboli. Phenomena named Factor V Lieden can produce a similar pathologic condition. Anti-coagulant deficiencies, including Factor V Lieden, are HIDDEN blood conditions that can allow blood clot development, especially with trauma to the tissue and circulatory system. It is proposed that all children between ages twelve to fourteen be checked hereditary deficiencies and Factor V Lieden complications. This would require the development of inexpensive assay equipment12. The present research focuses on the low cost production of Zymogen Protein C via purification from blood plasma Cohn Fraction IV-1. This process is difficult due to the several Homologous Vitamin K dependent proteins in the blood coagulation cascade. Traditional chromatography (ion exchange) cannot achieve the desired separation. Some more exotic technologies are very expensive so our work proposes to use Immobilized Metal Affinity Chromatography (IMAC). It is hoped to produce a lower cost product that can be used prophylactic ally to treat Protein C deficiencies and possibly other coagulation problems.